Comparison between single and double suture passing techniques in the suture bridge rotator cuff repair with a 2-mm tape: A simulation study using a three-dimensional finite element method.

BACKGROUND: Suture bridge repair has been widely used as one of the standard procedures in the arthroscopic rotator cuff repair. We compared the intratendinous stress distribution between single and double suture passing techniques in the suture bridge repair using a 2-mm tape and clarified the roles of tensioning in this procedure. METHODS: A board-like model of the supraspinatus tendon and humeral head was used in order to standardize conditions and exclude the influence of anatomical variations between individuals. Reattachment of the supraspinatus tendon to the bone was simulated using both single and double suture passing techniques for the suture bridge repair using a 2-mm tape. A tensile load was applied to the medial end of the tendon, and the stress distribution pattern was observed. Elastic analysis enabled comparison of the von Mises equivalent and maximum principal stresses between the single and double suture passing techniques. The tape configuration was subsequently translated 1 mm toward the insertion points of lateral anchors to simulate the tensioning maneuver. RESULTS: Although the distribution pattern of both the equivalent and the maximum principal stresses was similar for both models, areas with a high stress concentration were smaller in the single suture passing model than those in the double suture passing model. The equivalent stress concentrated within the tendon beneath the tapes as well as in the area between the crossing tapes and the lateral end of the tendon, whereas the maximum principal stress concentrated medial to the sites of suture penetration. CONCLUSIONS: Single suture passing technique can reduce the extent of intratendinous stress concentration compared with double suture passing technique, which might be beneficial to reduce the incidence of type 2 retear after suture bridge repair of rotator cuff tendon using a 2-mm tape.

Theory of particle transport phenomena during fatigue and time-dependent fracture of materials based on mesoscale dynamics and their practical applications.

In this work, the mesoscale mechanics of metals, which links their microscopic physics and macroscopic mechanics, was established. For practical applications, the laws for quantitatively predicting life of cycle and time-dependent fracture behavior such as fatigue, hydrogen embrittlement, and high-temperature creep were derived using particle transport phenomena theories such as dislocation group dynamics, hydrogen diffusion, and vacancy diffusion. Furthermore, these concepts were also applied for estimating the degree of viscoelastic deterioration of blood vessel walls, which is dominated by a time-dependent mechanism, and for the diagnosis of aneurysm accompanied by the viscoelastic deterioration of the blood vessel wall. In these theories, new mechanical indexes were derived as dominant factors for predicting the life of fatigue crack growth and the time-dependent fracture of notched specimens of materials such as hydrogen embrittlement and high-temperature creep. Furthermore, as an example of a practical application, these theories were applied to estimate the degree of viscoelastic deterioration and chaotic motions of blood vessel walls, which are closely related to blood vessel diseases such as atherosclerosis and aneurysm. Moreover, new indexes to diagnose them were also proposed for clinical applications.

Pre-clinical assessment of a prototype non-invasive diagnostic device to detect aortic aneurysms.

We have developed a non-invasive diagnostic device for treating thoracic aortic aneurysm that can be applied at a peripheral artery. This study aimed to examine how configuration and size of an aneurysm as well as endoluminal pressure affect our diagnostic device's ability to detect an aneurysm, using a pulsatile mock circulation. We created three different-sized (12, 16, and 20 mm) saccular and fusiform aneurysm models using silicone and incorporated them in a pulsatile perfusion circuit to evaluate vertical vessel wall velocity wave form at a location apart from the aneurysm. We also varied the pressure condition to evaluate the changes in the detected wave forms. In both fusiform and saccular aneurysm models, biphasic wave forms indicating the presence of aneurysm within the circuit were observed. Regarding aneurysm diameter, biphasic wave forms were observed in all aneurysm models. However, in the 12-mm model, which is relevant to the minimum diameter of clinical diagnostic criteria for an aneurysm relative to normal size, no biphasic waveform was detected when the endoluminal pressure was relatively low. In the 16- and 20-mm models, biphasic waveform was detected without being affected by the configuration and endoluminal pressure. The detectability of aneurysms within a pulsatile mock circulation using our non-invasive diagnostic device was not affected by the clinically relevant configuration and size of the aneurysm under slightly hypertensive endoluminal pressure condition. Low endoluminal pressure may lower the diagnostic sensitivity for relatively small saccular aneurysm.

Frequency and chaotic analysis of pulsatile motion of blood vessel wall related to aneurysm.

BACKGROUND/OBJECTIVE: In this research, using our proposed method, clinical measurements on the pulsatile velocity of blood vessel wall were conducted for cases with aneurysm. Furthermore, detailed analyses of frequency and attracter of trajectories of velocity of blood vessel wall were conducted. On the basis of these analyses, we tried to conduct unified clarification of the change and disturbance of frequency and wave form of pulsatile velocity of blood vessel wall caused by blood vessel diseases such as aneurysm. RESULTS: In the pulsation motion of blood vessel wall, vasomotion, which is a regular long periodic fluctuation of amplitude of the pulsatile velocity of blood vessel wall, was found to exist. Furthermore, the shift of its frequency into low frequency region was found to correspond well with an increase in I∗, an indicator of progressive degree of visco elasticity of blood vessel wall and it reflects the mechanical deterioration of blood vessel wall. This long periodic fluctuation of amplitude of the pulsatile velocity of blood vessel wall exists in the low frequency region that composes the frequency of the pulsatile velocity of blood vessel wall. On the other hand, wave forms in high frequency region that compose the frequency of pulsatile velocity of blood vessel wall were found to correspond well with each pulsatile velocity wave form of blood vessel wall itself and their disturbances caused by the existence of aneurysm was typically reflected in these wave forms. CONCLUSION: By dividing frequencies that compose the frequency of the pulsatile velocity of blood vessel wall into low and high frequency regions and conducting analyses at each region, the possibility of accurate selective detection of blood vessel diseases such as mechanical deterioration of blood vessel wall (low frequency region) and morphological change of blood vessel wall that is aneurysm (high frequency region) was indicated.

A novel diagnostic system for Doppler ultrasound of the peripheral arteries to detect the presence of thoracic aortic aneurysm.

OBJECTIVE: We aimed to develop a novel ultrasound system and examine its feasibility for noninvasively detecting thoracic aortic aneurysm (TAA) in clinical settings. METHODS: We developed a novel ultrasound system consisting of a modified console and data analysis algorithm. The exploratory study included 100 patients hospitalized for elective cardiovascular surgery. After admission, the arterial pulse waveform at the left carotid artery was acquired using the novel system. Based on these data, we inferred the presence of TAA based on arterial viscoelasticity and instability, which are reflected into the time-averaged trajectory of deformation of the blood vessel wall caused by disturbance of blood flow. Meanwhile, all patients underwent computed tomography as preoperative screening to confirm the presence of TAA. The sensitivity and specificity of TAA detection using the novel ultrasound system were calculated. RESULTS: The datasets from 37 patients were not suitable for analysis and were thus discarded. Based on computed tomography findings, 40 patients were categorized into the aneurysm group while 23 were judged not to have and aortic aneurysm. On the other hand, 44 patients were diagnosed as having TAA based on ultrasound findings obtained using the novel system. The overall sensitivity and specificity of the ultrasound system were 0.83 and 0.52, respectively. CONCLUSION: We successfully developed a novel system for noninvasive, ultrasound-based evaluation of the left carotid artery to detect TAA. Although improvements to the probe and diagnostic algorithm are warranted, this device has potential utility for mass screening to detect asymptomatic TAA as part of community-level healthcare programs.

Tight medial knot tying may increase retearing risk after transosseous equivalent repair of rotator cuff tendon.

BACKGROUND: Retearing mechanism after transosseous equivalent (TOE) rotator cuff repair has not been fully clarified yet. OBJECTIVE: The purposes of this study were to compare the stress distribution pattern in the tendon stump between knotted and knotless TOE repair and to investigate the role of suture tension applied during medial knot tying using a 3-dimensional finite element (3D-FE) method. METHODS: Both knotted and knotless TOE repairs were simulated on the 3D-FE human rotator cuff tear model. Elastic analysis was performed to compare the stress distribution pattern inside the tendon between the two models. The amount of compressive load applied to the medial-row sutures was then changed as 0, 20, 40, 60, 80, and 100 N in the knotted model. RESULTS: Knotted model demonstrated more distinct stress concentration inside the tendon around medial-row sutures than the knotless model. Mean von Mises equivalent stress in this area in the 0, 20, 40, 60, 80, and 100 N models was 0.26, 0.35, 0.50, 0.70, 1.11, and 1.14 MPa, respectively. CONCLUSIONS: In the knotted TOE repair, tight medial knot tying might cause a high stress concentration around medial knots, which may constitute one of the pathogenetic factors of postoperative retearing at this site.

Predicting failures of suture anchors used for rotator cuff repair: a CT-based 3-dimensional finite element analysis.

BACKGROUND: Failure of inserted anchors has been recognized as one of the major pathomechanisms of re-tearing after rotator cuff repair. OBJECTIVE: To predict the inserted anchor failure using CT-based 3-dimensional finite element method (CT/3D-FEM). METHODS: Among twenty patients who underwent rotator cuff repair, 5 had anchor failure (failed anchor group) and 15 had no anchor failure (stable anchor group). A 3D model of proximal humerus was developed for each patient based on the CT data. A virtual pullout testing of TWINFIX™ anchors inserted into bone at 6 different sites was performed using FEM. Then, mean failure load of 6 anchors for each patient was compared between two groups. Moreover, an optimal cut-off value of the mean failure load was determined for predicting anchor failure. RESULTS: The mean failure load in the failed anchor group (70.3 N) was significantly lower than that in the stable anchor group (119.0 N; p<0.0001). In our method, the optimum cut-off value of the mean failure load was 75.4 N. CONCLUSIONS: Failure of the inserted TWINFIX™ anchor could be predicted using CT/3D-FEM. In this method, there seemed to be a high risk of anchor failure in shoulders with a mean failure load of <75.4 N.

Viscoelastic Deterioration of the Carotid Artery Vascular Wall is a Possible Predictor of Coronary Artery Disease.

AIM: The viscoelastic properties of the artery are known to be altered in patients with vascular diseases. However, few studies have evaluated the viscoelasticity of the vascular wall in humans. We sought to investigate the degree of viscoelastic deterioration of the carotid artery and assess its clinical implications. METHODS: Between January 2011 and June 2013, patients in whom the toe-brachial index was measured at the vascular laboratory were included in this single-institute retrospective observational study. I(＊), a parameter of viscoelastic deterioration, was computed using a non-invasive ultrasonic Doppler effect sensor on the carotid artery. I(＊) is a non-dimensional value, and I(＊)>0 is considered abnormal. Other patient characteristics were identified and tested for correlations with I(＊). RESULTS: The study included 383 patients. The mean I(＊) value was 0.13 ± 0.22 with a normal distribution. Factors that increased the I(＊) value were a female sex (0.18 ± 0.23 vs. 0.10 ± 0.21, P<0.001), age ≥ 60 (0.14 ± 0.22 vs. 0.06 ± 0.23, P<0.05) and systolic blood pressure of >140 (0.15 ± 0.22 vs. 0.10 ± 0.22, P<0.05). I(＊) abnormality was a significant risk factor for coronary artery disease (OR 2.20, 95% CI 1.00-4.80, P<0.05) in a univariate analysis. In the multivariate analysis, I(＊) abnormality was also found to be an independent risk factor for coronary artery disease (OR 4.56, 95% CI 1.21-30.1, P<0.05). CONCLUSIONS: I(＊) may reflect the degree of atherosclerotic changes in the arterial wall and could possibly be used to predict coronary artery disease.

Correlation between the characteristics of acceleration and visco elasticity of artery wall under pulsatile flow conditions (physical meaning of I* as a parameter of progressive behaviors of atherosclerosis and arteriosclerosis).

Previously, I* parameter has been proposed to diagnose noninvasively the progressive degree of atherosclerosis which is considered to concern the discrimination of the progressive degree of visco elasticity of blood vessel wall. However, the detailed physical meaning of this parameter has not yet been clarified. In this paper, the theoretical analysis and experiments were conducted and the detailed physical meaning of I* parameter was clarified. The following results were obtained. I* parameter was found to well correlate with the progressive degree of visco elasticity of blood vessel wall characterized by the Ith* parameter derived based on the analysis of visco elasticity in this paper. That is, I* was found to have the physical meaning of representing the progressive degree of visco elasticity of blood vessel wall. On the basis of this results, using clinical data, two dimensional representation between the progressive degree of visco elasticity of blood vessel wall by I* and the decrease in the rigidity of blood vessel wall by PWV was found to be useful to conduct much more detailed diagnosis of atherosclerosis.

Frequency response of blood vessel wall with atherosclerosis and aneurysm.

This research was conducted to investigate frequency response of blood vessel wall. The principal frequency of blood vessel wall, f1 was found to decrease with progression of atherosclerosis and irregularity of the vibration trajectory of blood vessel wall was found to increase. When an aneurysm appeared, a new vibration wave was found to appear in the high frequency region, f2. When the aneurysm wall has enough strength, intensity of high frequency wave was found to increase. However, it decreases with decrease in the strength of aneurysm wall. The visco-elastic deterioration of blood vessel wall was found to well correlate with the changing characteristics of f1. A two-dimensional representation of f1 and f2 was conducted which tracks the progression of atherosclerosis and aneurysm. It will enable us to diagnose the introduction period of operation of blood vessel wall of atherosclerosis with an aneurysm.

The analysis and diagnosis of unstable behavior of the blood vessel wall with an aneurysm based on noise science.

Previously, one of the authors developed a noninvasive measurement method of acceleration and deceleration during the expansion process of the blood vessel wall under pulsatile pressure flow by measuring the strain rate of the blood vessel wall using a supersonic Doppler effect sensor aided by computer analysis (DPC method). In this paper, on the basis of the analysis of chaos theory, that is, the complexity of science, the unstable behavior of the blood vessel wall with an aneurysm was investigated by identifying the characteristic DPC wave forms induced by the onset and progression of aneurysm. These results showed that unstable dynamic behavior of the blood vessel wall occurs due to the progression of the aneurysm. Furthermore, using the theoretical analysis of chaos, this unstable behavior of the blood vessel wall was quantified and the fundamental principle of a noninvasive diagnostic method of the progressive degree of aneurysm was proposed.